The invention relates to a mechanism for the opening of the rapier heads of a weaving machine which works with rapiers.
With rapier weaving machines a problem exists for releasing the weft at the right moment from the receiving rapier at the completion of the weft insertion. If the weft is released too early by the receiving rapier, then the weft springs back into the shed and then a piece of weft is missing in the fabric on that fabric side. Weft faults develop because of this and the fabric obtained is not of desired quality. If on the other hand the weft is held too long by the receiving rapier, then long weft ends develop outside the weave edges, which causes the weft loss to increase.
With rapier weaving machines this means that the machines should be able to time the release of the weft by the receiving rapier at the right moment so that the above mentioned disadvantages do not occur.
More over double rapier weaving machines are weaving various pile height this means that the rapiers should have different positions in height and that the distance between the rapiers need to be set. Hence there is a requirement to make the control of rapier heads also adjustable in position and in mutual distance, according to the rapier distance and pile height to be woven.
In order to remedy this the opening of the rapier heads is controlled by a system of rod linkages. The control of the rod heads is assured by a cam disk, sometimes also with a spring return.
This kinematic chain is however too long, and too much play develops at the end lever as a result of the various plays in the numerous pivots and bearings. Namely vibrations develop in the end lever which bring about difficulties in the opening of the receiving rapier. These vibrations cause wear and tear of the rod heads which therefore have to be replaced.
Furthermore this solution no longer satisfies the present working speed to be achieved by the weaving machines, in particular for double rapier weaving machines this is 400 r.p.m.